1. Technical Field
Embodiments relate to an image pickup lens and, more particularly, to an image pickup lens, constituent lenses of which have the same index of refraction and achieve a compact size and enhanced performance.
2. Related Art
The Recently, conventional film cameras have been replaced with camera modules for portable terminals using a compact solid-state image pickup device (e.g., a Charge Coupled Device (CCD) or a Complementary Metal Oxide Semiconductor (CMOS)), Digital Still Cameras (DSCs), camcorders, PC cameras (i.e. image pickup apparatuses attached to personal computers) and the like. These image pickup apparatuses are gradually becoming leaner and smaller.
With this tendency, although a light receiving device, such as a CCD, mounted in a compact image pickup apparatus is being made smaller, an image pickup lens of the image pickup apparatus still occupies the largest volume of the image pickup apparatus.
Thus, the major issue with regard to a leaner and smaller configuration of the image pickup apparatus is the image pickup lens that forms an image of an object.
Here, problems are not only to merely realize a compact size of the image pickup lens, but also to achieve high performance of the image pickup lens corresponding to high performance of the light receiving device.
However, the compact image pickup lens is inevitably located close to the light receiving device, which problematically causes light to be obliquely incident on an image surface of the image pickup apparatus. This results in insufficient light concentration of the image pickup lens as well as extreme variation in the brightness of an image from the center to the periphery of the image.
Increasing the number of lenses in consideration of the above-described problems, however, inevitably increases the size of the image pickup apparatus and this is also disadvantageous in terms of costs.
Therefore, there is a need to achieve a high performance image pickup lens in consideration of manufacturing cost.